In 1993, researchers in Chad unearthed a 3.5-million-year-old hominid lower jaw fragment and a few attached teeth. Based on the fossils' age, many anthropologists think the bones belonged to Australopithecus afarensis. But the specimen was found more than 2,400 kilometres farther west than any other afarensis bones, and subtle differences in the size and shape of the fossils led the discoverers to conclude they had found a new species. They named it Australopithecus bahrelghazali after the Bahr el Ghazal valley where the bones were recovered. Since then, researchers haven't found any other bahrelghazali fossils, and its species' status remains controversial.
With just a jaw and teeth, there's not too much scientists can say about what Australopithecus bahrelghazali looked like or how it lived its life, but analysing the teeth's chemistry is one way to assess what the species ate.
Julia Lee-Thorp of Oxford University and colleagues have revealed that Australopithecus bahrelghazali mainly ate plants - probably grasses and sedges - and like modern baboons that live on savannahs, probably different parts of these plants, including underground tubers and bulbs. Based on the other types of animals found near the hominid, the researchers say bahrelghazali made its home in an open grassland, with few trees, near a lake.
The results mean that by 3.5 million years ago hominids were probably already capable of eating a variety of foods depending on what was locally available. Being a food generalist may have allowed Australopithecus bahrelghazali to explore new environments and leave behind the forests in which earlier hominids and their ancestors had resided.

Edited from ScienceNews (12 November 2012), Smithsonian.com (14 November 2012)